Decellularization for whole organ bioengineering

Focus on seed cells: stem cells in 3D bioprinting of corneal grafts

Corneal opacity is one of the leading causes of severe vision impairment. Corneal transplantation is the dominant therapy for irreversible corneal blindness. However, there is a worldwide shortage of donor grafts and consequently an urgent demand for alternatives. Three-dimensional (3D) bioprinting is an innovative additive manufacturing technology for high-resolution distribution of bioink to construct human tissues. The technology has shown great promise in the field of bone, cartilage and skin tissue construction. 3D bioprinting allows precise structural construction and functional cell printing, which makes it possible to print personalized full-thickness or lamellar corneal layers. Seed cells play an important role in producing corneal biological functions. And stem cells are potential seed cells for corneal tissue construction. In this review, the basic anatomy and physiology of the natural human cornea and the grafts for keratoplasties are introduced. Then, the applications of 3D bioprinting techniques and bioinks for corneal tissue construction and their interaction with seed cells are reviewed, and both the application and promising future of stem cells in corneal tissue engineering is discussed. Finally, the development trends requirements and challenges of using stem cells as seed cells in corneal graft construction are summarized, and future development directions are suggested.

A comprehensive review on nanocomposite biomaterials based on gelatin for bone tissue engineering

The creation of a suitable scaffold is a crucial step in the process of bone tissue engineering (BTE). The scaffold, acting as an artificial extracellular matrix, plays a significant role in determining the fate of cells by affecting their proliferation and differentiation in BTE. Therefore, careful consideration should be given to the fabrication approach and materials used for scaffold preparation. Natural polypeptides such as gelatin and collagen have been widely used for this purpose. The unique properties of nanoparticles, which vary depending on their size, charge, and physicochemical properties, have demonstrated potential in solving various challenges encountered in BTE. Therefore, nanocomposite biomaterials consisting of polymers and nanoparticles have been extensively used for BTE. Gelatin has also been utilized in combination with other nanomaterials to apply for this purpose. Composites of gelatin with various types of nanoparticles are particularly promising for creating scaffolds with superior biological and physicochemical properties. This review explores the use of nanocomposite biomaterials based on gelatin and various types of nanoparticles together for applications in bone tissue engineering.

Processing and post-processing of fish skin as a novel material in tissue engineering

As a natural material, fish skin contains significant amounts of collagen I and III, and due to its biocompatible nature, it can be used to regenerate various tissues and organs. To use fish skin, it is necessary to perform the decellularization process to avoid the immunological response of the host body. In the process of decellularization, it is crucial to conserve the extracellular matrix (ECM) three-dimensional (3D) structure. However, it is known that decellularization methods may also damage ECM strands arrangement and structure. Moreover, after decellularization, the post-processing of fish skin improves its mechanical and biological properties and preserves its 3D design and strength. Also, sterilization, which is one of the post-processing steps, is mandatory in pre-clinical and clinical settings. In this review paper, the fish skin decellularization methods performed and the various post-processes used to increase the performance of the skin have been studied. Moreover, multiple applications of acellular fish skin (AFS) and its extracted collagen have been reviewed.

Vascular reconstruction of the decellularized biomatrix for whole-organ engineering-a critical perspective and future strategies

Whole-organ re-engineering is the most challenging goal yet to be achieved in tissue engineering and regenerative medicine. One essential factor in any transplantable and functional tissue engineering is fabricating a perfusable vascular network with macro- and micro-sized blood vessels. Whole-organ development has become more practical with the use of the decellularized organ biomatrix (DOB) as it provides a native biochemical and structural framework for a particular organ. However, reconstructing vasculature and re-endothelialization in the DOB is a highly challenging task and has not been achieved for constructing a clinically transplantable vascularized organ with an efficient perfusable capability. Here, we critically and articulately emphasized factors that have been studied for the vascular reconstruction in the DOB. Furthermore, we highlighted the factors used for vasculature development studies in general and their application in whole-organ vascular reconstruction. We also analyzed in detail the strategies explored so far for vascular reconstruction and angiogenesis in the DOB for functional and perfusable vasculature development. Finally, we discussed some of the crucial factors that have been largely ignored in the vascular reconstruction of the DOB and the future directions that should be addressed systematically.

ECM-based bioactive microencapsulation significantly improves islet function and graft performance

Microencapsulation is a promising strategy to prolong the survival and function of transplanted pancreatic islets for diabetes therapy, albeit its translation has been impeded by incoherent graft performance. The use of decellularized ECM has lately gained substantial research momentum due to its innate capacity to augment the function of cells originating from the same tissue type. In the present study, the advantages of both these approaches are leveraged in a porcine pancreatic ECM (pECM)-based microencapsulation platform, thus significantly enhancing murine pancreatic islet performance. pECM-encapsulated islets sustain high insulin secretion levels in vitro, surpassing those of islets encapsulated in conventional alginate microcapsules. Moreover, pECM-encapsulated islet cells proliferate and produce an enriched intra-islet ECM framework, displaying a distinctive structural rearrangement. The beneficial effect of pECM encapsulation is further reinforced by the temporary protection against cytokine-induced cytotoxicity. In-vivo, this platform significantly improves glucose tolerance and achieves glycemic correction in 100% of immunocompetent diabetic mice without any immunosuppression, compared to only 50% mice achieved glycemic correction by alginate encapsulation. Altogether, the results presented herein reveal that pECM-based microencapsulation offers a natural pancreatic niche that can restore the function of isolated pancreatic islets and deliver them safely, avoiding the need for immunosuppression. STATEMENT OF SIGNIFICANCE: Aiming to improve pancreatic islet transplantation outcomes in diabetic patients, we developed a microencapsulation platform based on pancreatic extracellular matrix (pECM). In these microcapsules the islets are entrapped within a pECM hydrogel that mimics the natural pancreatic microenvironment. We show that pECM encapsulation supports the islets' viability and function in culture, and provides temporal protection against cytokine-induced stress. In a diabetic mouse model, pECM encapsulation significantly improved glucose tolerance and achieved glycemic correction without any immunosuppression. These results reveal the potential of pECM encapsulation as a viable treatment for diabetes, providing a solid scientific basis for more advanced preclinical studies.

Extracellular Matrix-Based and Electrospun Scaffolding Systems for Vaginal Reconstruction

Congenital vaginal anomalies and pelvic organ prolapse affect different age groups of women and both have significant negative impacts on patients' psychological well-being and quality of life. While surgical and non-surgical treatments are available for vaginal defects, their efficacy is limited, and they often result in long-term complications. Therefore, alternative treatment options are urgently needed. Fortunately, tissue-engineered scaffolds are promising new treatment modalities that provide an extracellular matrix (ECM)-like environment for vaginal cells to adhere, secrete ECM, and be remodeled by host cells. To this end, ECM-based scaffolds or the constructs that resemble ECM, generated by self-assembly, decellularization, or electrospinning techniques, have gained attention from both clinicians and researchers. These biomimetic scaffolds are highly similar to the native vaginal ECM and have great potential for clinical translation. This review article aims to discuss recent applications, challenges, and future perspectives of these scaffolds in vaginal reconstruction or repair strategies.

Whole-Heart Tissue Engineering and Cardiac Patches: Challenges and Promises

Despite all the advances in preventing, diagnosing, and treating cardiovascular disorders, they still account for a significant part of mortality and morbidity worldwide. The advent of tissue engineering and regenerative medicine has provided novel therapeutic approaches for the treatment of various diseases. Tissue engineering relies on three pillars: scaffolds, stem cells, and growth factors. Gene and cell therapy methods have been introduced as primary approaches to cardiac tissue engineering. Although the application of gene and cell therapy has resulted in improved regeneration of damaged cardiac tissue, further studies are needed to resolve their limitations, enhance their effectiveness, and translate them into the clinical setting. Scaffolds from synthetic, natural, or decellularized sources have provided desirable characteristics for the repair of cardiac tissue. Decellularized scaffolds are widely studied in heart regeneration, either as cell-free constructs or cell-seeded platforms. The application of human- or animal-derived decellularized heart patches has promoted the regeneration of heart tissue through in vivo and in vitro studies. Due to the complexity of cardiac tissue engineering, there is still a long way to go before cardiac patches or decellularized whole-heart scaffolds can be routinely used in clinical practice. This paper aims to review the decellularized whole-heart scaffolds and cardiac patches utilized in the regeneration of damaged cardiac tissue. Moreover, various decellularization methods related to these scaffolds will be discussed.

Functional acellular matrix for tissue repair

In view of their low immunogenicity, biomimetic internal environment, tissue- and organ-like physicochemical properties, and functionalization potential, decellularized extracellular matrix (dECM) materials attract considerable attention and are widely used in tissue engineering. This review describes the composition of extracellular matrices and their role in stem-cell differentiation, discusses the advantages and disadvantages of existing decellularization techniques, and presents methods for the functionalization and characterization of decellularized scaffolds. In addition, we discuss progress in the use of dECMs for cartilage, skin, nerve, and muscle repair and the transplantation or regeneration of different whole organs (e.g., kidneys, liver, uterus, lungs, and heart), summarize the shortcomings of using dECMs for tissue and organ repair after refunctionalization, and examine the corresponding future prospects. Thus, the present review helps to further systematize the application of functionalized dECMs in tissue/organ transplantation and keep researchers up to date on recent progress in dECM usage.

The application of 3D bioprinting in urological diseases

Urologic diseases are commonly diagnosed health problems affecting people around the world. More than 26 million people suffer from urologic diseases and the annual expenditure was more than 11 billion US dollars. The urologic cancers, like bladder cancer, prostate cancer and kidney cancer are always the leading causes of death worldwide, which account for approximately 22% and 10% of the new cancer cases and death, respectively. Organ transplantation is one of the major clinical treatments for urological diseases like end-stage renal disease and urethral stricture, albeit strongly limited by the availability of matching donor organs. Tissue engineering has been recognized as a highly promising strategy to solve the problems of organ donor shortage by the fabrication of artificial organs/tissue. This includes the prospective technology of three-dimensional (3D) bioprinting, which has been adapted to various cell types and biomaterials to replicate the heterogeneity of urological organs for the investigation of organ transplantation and disease progression. This review discusses various types of 3D bioprinting methodologies and commonly used biomaterials for urological diseases. The literature shows that advances in this field toward the development of functional urological organs or disease models have progressively increased. Although numerous challenges still need to be tackled, like the technical difficulties of replicating the heterogeneity of urologic organs and the limited biomaterial choices to recapitulate the complicated extracellular matrix components, it has been proved by numerous studies that 3D bioprinting has the potential to fabricate functional urological organs for clinical transplantation and in vitro disease models.

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Outline the advantages and characteristics of 3D printing compared with traditional methods for urological diseases.

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Guide the selection of 3D bioprinting technology and material in urological tissue engineering.

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Discuss the challenges and future perspectives of 3D bioprinting in urological diseases and clinical translation.

Lacrimal gland regeneration: The unmet challenges and promise for dry eye therapy

DED (Dry eye disease) is a common multifactorial disease of the ocular surface and the tear film. DED has gained attention globally, with millions of people affected.. Although treatment strategies for DED have shifted towards Tear Film Oriented Therapy (TFOT), all the existing strategies fall under standard palliative care when addressed as a long-term goal. Therefore, different approaches have been explored by various groups to uncover alternative treatment strategies that can contribute to a full regeneration of the damaged lacrimal gland. For this, multiple groups have investigated the role of lacrimal gland (LG) cells in DED based on their regenerating, homing, and differentiating capabilities. In this review, we discuss in detail therapeutic mechanisms and regenerative strategies that can potentially be applied for lacrimal gland regeneration as well as their therapeutic applications. This review mainly focuses on Aqueous Deficiency Dry Eye Disease (ADDE) caused by lacrimal gland dysfunction and possible future treatment strategies. The current key findings from cell and tissue-based regenerative therapy modalities that could be utilised to achieve lacrimal gland tissue regeneration are summarized. In addition, this review summarises the available literature from in vitro to in vivo animal studies, their limitations in relation to lacrimal gland regeneration and the possible clinical applications. Finally, current issues and unmet needs of cell-based therapies in providing complete lacrimal gland tissue regeneration are discussed.

Applications of Tissue Decellularization Techniques in Ventricular Myocardial Biofabrication

Ischemic heart disease is the leading cause of death around the world, and though the advent of coronary revascularization has revolutionized its treatment, many patients who sustain ischemic injury to the heart will go on to develop heart failure. Biofabrication of ventricular myocardium for replacement of irreversibly damaged ischemic myocardium is sought after as a potential therapy for ischemic heart failure, though challenges in reliably producing this biomaterial have limited its clinical application. One method that shows promise for generation of functional myocardium is the use of tissue decellularization to serve as a scaffold for biofabrication. This review outlines the methods, materials, challenges, and prospects of tissue decellularization techniques for ventricular myocardium biofabrication. Decellularization aims to preserve the architecture and composition of the extracellular matrix of the tissue it is applied to, allowing for the subsequent implantation of stem cells of the desired cell type. Decellularization can be achieved with multiple reagents, most of which have detergent properties. A variety of cell types can be implanted in the resulting scaffold, including cardiac progenitor cells, and embryonic or induced pluripotent stem cells to generate a range of tissue, from patches to beating myocardium. The future of this biofabrication method will likely emphasize patient specific tissue engineering to generate complex 3-dimensional constructs that can replace dysfunctional cardiac structures.

Matrisome provides a supportive microenvironment for oral squamous cell carcinoma progression

Oral squamous cell carcinoma (OSCC) is a common pernicious tumor in the head and neck regions. However, the function of tumor extracellular matrix (ECM) has not been elucidated. A tissue engineering method was applied for remodeling ECM through decellularization. The cellular components were removed, and the biological composition was mostly preserved. Proteomics was performed to analyze the characterization between normal and tumor ECM. According to LC-MS/MS results, 26 proteins just showed in tumor ECM, and 14 proteins only showed in late-stage tumor ECM. KEGG pathway analysis showed that most variant proteins were linked to metabolic regulation and tumor immunity (such as SCC-Ag1, LOX). To affirm the influence of tumor ECM on the progression of OSCC, tumor cells and macrophages were co-cultured with ECM scaffold. Marked differences in proliferation, apoptosis, and migration of OSCC cells were observed between tumor and normal ECM. Tumor ECM polarized macrophages towards an anti-inflammatory phenotype (higher IL-10 and CD68, and relatively lower CD86 and IL1-β). Collectively, these findings suggest that tumor ECM served as a permissive role in OSCC progression. SIGNIFICANCE: The variation between OSCC ECM and normal ECM confirm tumor ECM plays a significant role in OSCC deterioration, which is conducive to exploring the occurrence and progression mechanisms of OSCC, and further improving the curative effect of this disease.

Two new applications in the study of angiogenesis the CAM assay: Acellular scaffolds and organoids

The chick embryo chorioallantoic membrane (CAM) is a rich vascularized extraembryonic membrane that is commonly used as an in vivo experimental model to study molecules with angiogenic and anti-angiogenic activity, tumor growth and metastasis. Among other applications of the CAM assay, more recently this assay has been used for the study of acellular scaffolds and of organoids, and of their angiogenic capacity. The aim of this review article is to summarize the literature data concerning these two new applications of the CAM assay and to underline the advantages of this assay.

Biomechanics of Additively Manufactured Metallic Scaffolds-A Review

This review paper is related to the biomechanics of additively manufactured (AM) metallic scaffolds, in particular titanium alloy Ti6Al4V scaffolds. This is because Ti6Al4V has been identified as an ideal candidate for AM metallic scaffolds. The factors that affect the scaffold technology are the design, the material used to build the scaffold, and the fabrication process. This review paper includes thus a discussion on the design of Ti6A4V scaffolds in relation to how their behavior is affected by their cell shapes and porosities. This is followed by a discussion on the post treatment and mechanical characterization including in-vitro and in-vivo biomechanical studies. A review and discussion are also presented on the ongoing efforts to develop predictive tools to derive the relationships between structure, processing, properties and performance of powder-bed additive manufacturing of metals. This is a challenge when developing process computational models because the problem involves multi-physics and is of multi-scale in nature. Advantages, limitations, and future trends in AM scaffolds are finally discussed. AM is considered at the forefront of Industry 4.0, the fourth industrial revolution. The market of scaffold technology will continue to boom because of the high demand for human tissue repair.

Regenerative Engineering: Current Applications and Future Perspectives

Many pathologies, congenital defects, and traumatic injuries are untreatable by conventional pharmacologic or surgical interventions. Regenerative engineering represents an ever-growing interdisciplinary field aimed at creating biological replacements for injured tissues and dysfunctional organs. The need for bioengineered replacement parts is ubiquitous among all surgical disciplines. However, to date, clinical translation has been limited to thin, small, and/or acellular structures. Development of thicker tissues continues to be limited by vascularization and other impediments. Nevertheless, currently available materials, methods, and technologies serve as robust platforms for more complex tissue fabrication in the future. This review article highlights the current methodologies, clinical achievements, tenacious barriers, and future perspectives of regenerative engineering.

Generation of a Biomimetic Substitute of the Corneal Limbus Using Decellularized Scaffolds

Patients with severe limbal damage and limbal stem cell deficiency are a therapeutic challenge. We evaluated four decellularization protocols applied to the full-thickness and half-thickness porcine limbus, and we used two cell types to recellularize the decellularized limbi. The results demonstrated that all protocols achieved efficient decellularization. However, the method that best preserved the transparency and composition of the limbus extracellular matrix was the use of 0.1% SDS applied to the half-thickness limbus. Recellularization with the limbal epithelial cell line SIRC and human adipose-derived mesenchymal stem cells (hADSCs) was able to generate a stratified epithelium able to express the limbal markers p63, pancytokeratin, and crystallin Z from day 7 in the case of SIRC and after 14-21 days of induction when hADSCs were used. Laminin and collagen IV expression was detected at the basal lamina of both cell types at days 14 and 21 of follow-up. Compared with control native limbi, tissues recellularized with SIRC showed adequate picrosirius red and alcian blue staining intensity, whereas limbi containing hADSCs showed normal collagen staining intensity. These preliminary results suggested that the limbal substitutes generated in this work share important similarities with the native limbus and could be potentially useful in the future.

Decellularization Methods of Vagina and Cervix in Tissue Engineering

The vagina is a fibromuscular elastic tubular tract that connects the cervix with the outer genitals and has an important function discharging uterine secretions, sexual intercourse and acts as the passage for the full-term fetus. Currently, a new field of investigation which aims to design tissues and organs similar to their native origin has been developed recently and was named regenerative medicine (tissue engineering and bioengineering). Malformations in cervix tissue represent a hard challenge for medicine. Experts in bioengineering have tried to reconstruct vaginas or cervix with the aim to achieve cervicovaginal disorders, most of them with congenital cause. However, only few research groups have launched themselves upon the decellularization. The aim of this chapter is investigating the decellularization methods for cervix and vaginal tissues.

Decellularization of kidney tissue: comparison of sodium lauryl ether sulfate and sodium dodecyl sulfate for allotransplantation in rat

An automatic decellularization device was developed to perfuse and decellularize male rats' kidneys using both sodium lauryl ether sulfate (SLES) and sodium dodecyl sulfate (SDS) and to compare their efficacy in kidney decellularization and post-transplantation angiogenesis. Kidneys were perfused with either 1% SDS solution for 4 h or 1% SLES solution for 6 h. The decellularized scaffolds were stained with hematoxylin and eosin, periodic acid Schiff, Masson's trichrome, and Alcian blue to determine cell removal and glycogen, collagen, and glycosaminoglycan contents, respectively. Moreover, scanning electron microscopy was performed to evaluate the cell removal and preservation of microarchitecture of both SDS and SLES scaffolds. Additionally, DNA quantification assay was applied for all groups in order to measure residual DNA in the scaffolds and normal kidney. In order to demonstrate biocompatibility of the decellularized scaffolds, human umbilical cord mesenchymal stromal/stem cells (hUC-MSCs) were seeded on the scaffolds. In addition, the allotransplantation was performed in back muscle and angiogenesis was evaluated. Complete cell removal in both SLES and SDS groups was observed in scanning electron microscopy and DNA quantification assays. Moreover, the extracellular matrix (ECM) architecture of rat kidney in the SLES group was significantly preserved better than the SDS group. The hUC-MSCs were successfully migrated from the cell culture plate surface into the SDS and SLES decellularized scaffolds. The formation of blood vessels was observed in the kidney in both SLES and SDS decellularized kidneys. The better preservation of ECM than SDS introduces SLES as the solvent of choice for kidney decellularization.

Application of iPSCs derived pancreatic β-like cells using pancreatic bio-scaffold

This study aimed toengineer a pancreatic tissue. Intact rat pancreases were successfully decellularized, and were reseeded with human-induced pluripotent stem cells using different 2D and 3D culture growth factors. The differentiation process was assessed for the presence of a pancreas-like tissue. The histology and SEM analysis revealed cell attachment in all samples, except for the Exp4, and the Flow-cytometry provided 87% viability for the differentiated cells. In Exp1, PDX1 with the positive expression of 2.87±0.06 was dramatically higher than Exp2 with a 2.44±0.06 reaction. NGN3-reactions were 8±0.1 and 6.6±0.2 in Exp1 and Exp2 at P < 0.05, respectively. C-peptide with the expression of 7.5±0.7 in Exp3 was almost equal to that in Exp1 and Exp2. Glucagon (5.1±1) and PDX1 (3.2±0.82) in Exp3 indicated no significant difference. The significant upregulations of pancreatic endocrine markers (PDX1 and NGN3), and the cell-specific glucose transporter (GLUT2) were observed in the differentiated IPCs in the 3D culture of Exp2 after 21 days. The highest insulin and C-peptide concentrations were observed in Exp2. In Exp3, insulin secretion in response to high glucose and 10 mM arginine was 42.43 ±6.34 μU/ml. A decellularized pancreas in the presence of hiPSCs and growth factors could be efficiently used as a natural scaffold.

Optimizing Decellularization Strategies for the Efficient Production of Whole Rat Kidney Scaffolds

BACKGROUND

Renal dysfunction remains a global issue, with chronic kidney disease being the 18th most leading cause of death, worldwide. The increased demands in kidney transplants, led the scientific society to seek alternative strategies, utilizing mostly the tissue engineering approaches. Unlike to perfusion decellularization of kidneys, we proposed alternative decellularization strategies to obtain acellular kidney scaffolds. The aim of this study was the evaluation of two different decellularization approaches for producing kidney bioscaffolds.

METHODS

Rat kidneys from Wistar rats, were submitted to decellularization, followed two different strategies. The decellularization solutions used in both approaches were the same and involved the use of 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate and sodium dodecyl sulfate buffers for 12 h each, followed by incubation in a serum medium. Both approaches involved 3 decellularization cycles. Histological analysis, biochemical and DNA quantification were performed. Cytotoxicity assay and repopulation of acellular kidneys were also applied.

RESULTS

Histological, biochemical and DNA quantification confirmed that the 2nd approach had the best outcome regarding the kidney composition and cell elimination. Acellular kidneys from both approaches were successfully recellularized.

CONCLUSION

Based on the above data, the production of kidney scaffolds with the proposed cost- effective decellularization approaches, was efficient.

Detection of the residual concentration of sodium dodecyl sulfate in the decellularized whole rabbit kidney extracellular matrix

To optimize rabbit kidney decellularization protocol, using sodium dodecyl sulfate (SDS) as a commonly used detergent, a methylene blue based assay was employed for detecting the minimum nontoxic SDS level for future cell seeding. The rabbit kidney tissues were decellularized with the perfusion-based method and underwent several investigations to determine the efficacy of decellularization in preserving the extracellular matrix (ECM) and cell removal. SDS detection was performed by incubating with methylene blue and subsequent extraction with chloroform. MTT (3-(4, 5-dimethylthiazol-2-yr)-2,5-diphenyltetrazolium bromide) assay and SDS release were also evaluated during the entire process. After the first washing cycle, SDS concentration was 0.036, in 500 mL of the washing liquid, which slowly decreased and reached to 0.009 % after at the end of seventh washing cycle. In the 9th cycle, SDS was gradually decreased and reached to 0.003 %. SDS was significantly released after one week of incubation which ceased after ten washing cycles. The results of MTT assay demonstrated that different cells exhibited various sensitivity levels when exposed to serial concentrations of SDS. Human embryonic kidney cells (HEK293) with 0.003 % threshold for cellular toxicity and 87.4 % cell viability were more resistant compared with mesenchymal stem cells with 0.001 % threshold and 85.4 % cell viability. Colorimetric assay with methylene blue is a straightforward and non-invasive method to detect residual SDS present in tissue and can also prevent ECM destruction after several washings for detergent removal from decellularized tissues.

Distinct chemical composition and enzymatic treatment induced human endothelial cells survival in acellular ovine aortae

Objective

The current experiment aimed to assess the impact of detergents such as 3% Triton X-100, 1% peracetic acid, 1% Tween-20, and 1% SDS in combination with Trypsin–EDTA on acellularization of ovine aortae after 7 days.

Results

Hematoxylin–Eosin staining showed an appropriate acellularization rate in ovine aortae, indicated by a lack of cell nuclei in the tunica media layer. DAPI staining confirmed the lack of nuclei in the vascular wall after being exposed to the combination of chemical and enzymatic solutions. Verhoeff-Van Gieson staining showed that elastin fibers were diminished in acellular samples compared to the control group while collagen stands were unchanged. CCK-8 survival assay showed enhanced viability in human umbilical vein endothelial cells 5 days after being cultured on decellularized samples compared to the cells cultured on a plastic surface (p < 0.05). SEM imaging showed flattening of endothelial cells on the acellular surface.

A Review of Recent Advances in 3D Bioprinting With an Eye on Future Regenerative Therapies in Veterinary Medicine

3D bioprinting is a rapidly evolving industry that has been utilized for a variety of biomedical applications. It differs from traditional 3D printing in that it utilizes bioinks comprised of cells and other biomaterials to allow for the generation of complex functional tissues. Bioprinting involves computational modeling, bioink preparation, bioink deposition, and subsequent maturation of printed products; it is an intricate process where bioink composition, bioprinting approach, and bioprinter type must be considered during construct development. This technology has already found success in human studies, where a variety of functional tissues have been generated for both in vitro and in vivo applications. Although the main driving force behind innovation in 3D bioprinting has been utility in human medicine, recent efforts investigating its veterinary application have begun to emerge. To date, 3D bioprinting has been utilized to create bone, cardiovascular, cartilage, corneal and neural constructs in animal species. Furthermore, the use of animal-derived cells and various animal models in human research have provided additional information regarding its capacity for veterinary translation. While these studies have produced some promising results, technological limitations as well as ethical and regulatory challenges have impeded clinical acceptance. This article reviews the current understanding of 3D bioprinting technology and its recent advancements with a focus on recent successes and future translation in veterinary medicine.

Three-dimensional decellularized tumor extracellular matrices with different stiffness as bioengineered tumor scaffolds

In the three-dimensional (3D) tumor microenvironment, matrix stiffness is associated with the regulation of tumor cells behaviors. In vitro tumor models with appropriate matrix stiffness are urgently desired. Herein, we prepare 3D decellularized extracellular matrix (DECM) scaffolds with different stiffness to mimic the microenvironment of human breast tumor tissue, especially the matrix stiffness, components and structure of ECM. Furthermore, the effects of matrix stiffness on the drug resistance of human breast cancer cells are explored with these developed scaffolds as case studies. Our results confirm that DECM scaffolds with diverse stiffness can be generated by tumor cells with different lysyl oxidase (LOX) expression levels, while the barely intact structure and major components of the ECM are maintained without cells. This versatile 3D tumor model with suitable stiffness can be used as a bioengineered tumor scaffold to investigate the role of the microenvironment in tumor progression and to screen drugs prior to clinical use to a certain extent.

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Novel 3D bioengineered tumor scaffolds with different stiffness were developed.

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Cells with different LOX expression levels were used to generate tumor tissue.

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DECM scaffold has good cytocompatibility.

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DECM with high stiffness promotes the resistance of MDA-MB-231 cells to cisplatin.

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DECM with high stiffness increases the expression of Bcl-2 and ABCB1.

3D Bioprinting of In Vitro Models Using Hydrogel-Based Bioinks

Coronavirus disease 2019 (COVID-19), which has recently emerged as a global pandemic, has caused a serious economic crisis due to the social disconnection and physical distancing in human society. To rapidly respond to the emergence of new diseases, a reliable in vitro model needs to be established expeditiously for the identification of appropriate therapeutic agents. Such models can be of great help in validating the pathological behavior of pathogens and therapeutic agents. Recently, in vitro models representing human organs and tissues and biological functions have been developed based on high-precision 3D bioprinting. In this paper, we delineate an in-depth assessment of the recently developed 3D bioprinting technology and bioinks. In particular, we discuss the latest achievements and future aspects of the use of 3D bioprinting for in vitro modeling.

Analysis of structural components of decellularized scaffolds in renal fibrosis

Chronic kidney disease has been recognized as a major public health problem worldwide and renal fibrosis is a common pathological process occurring in chronic renal failure. It is very promising to find the strategies to slow or even prevent the progression of fibrosis. This study focused on whether renal fibrosis decellularized scaffolds has the potential to be a model of cellular mechanisms of tissue fibrosis or donors for tissue engineering. In order to evaluate the feasibility of decellularized scaffolds derived from pathological kidneys, histology, proteomics and ELISA will be used to analysis the changes in the structure and main components of fibrotic tissue. The fibrosis model in this paper was induced by adenine-fed and the results showed that the structure of fibrotic scaffold was changed and some protein were up-regulated or down-regulated, but the cytokines associated with renal regeneration after injury were remained. In cell experiments, endothelial progenitor cells proliferated well, which proved that the fibrotic scaffolds have non-cytotoxic. All these conclusions indicate that the renal fibrosis decellularized scaffolds model has the ability to study fibrosis mechanism and the potential to be engineering donors as well as normal scaffolds.

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A study model of the mechanism of renal fibrosis from natural sources.

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Adenine-induced renal fibrosis with a cytopathic scaffold preserves important cytokines.

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There was no significant difference in cytokine content with natural scaffolds.

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Heat maps of differentially expressed proteins from subcellular localization.

Decellularization Methods of Uterus in Tissue Engineering

A new field of investigation which aims to design tissues and organs similar to their native origin has been developed recently, named as regenerative medicine (tissue engineering and bio-engineering). Uterus is the main organ for regeneration and contributes in the fertility. At an ultimate level, the uterus plays a role in embryo implantation, sperm migration and fetal nutrition. Uterine congenital anomalies, attained uterine lesions and immune system disorders may affect such uterine functions preventing successful pregnancy. Due to following reasons, it is essential to consider regenerative medicine as a new approach for the treatment of uterine dysfunctions to overcome the failures that cannot be treated with clinical medication.

The useful agent to have an ideal biological scaffold

Tissue engineering which is applied in regenerative medicine has three basic components: cells, scaffolds and growth factors. This multidisciplinary field can regulate cell behaviors in different conditions using scaffolds and growth factors. Scaffolds perform this regulation with their structural, mechanical, functional and bioinductive properties and growth factors by attaching to and activating their receptors in cells. There are various types of biological extracellular matrix (ECM) and polymeric scaffolds in tissue engineering. Recently, many researchers have turned to using biological ECM rather than polymeric scaffolds because of its safety and growth factors. Therefore, selection the right scaffold with the best properties tailored to clinical use is an ideal way to regulate cell behaviors in order to repair or improve damaged tissue functions in regenerative medicine. In this review we first divided properties of biological scaffold into intrinsic and extrinsic elements and then explain the components of each element. Finally, the types of scaffold storage methods and their advantages and disadvantages are examined.

Utility of Air Bladder-Derived Nanostructured ECM for Tissue Regeneration

Exploration for ideal bone regeneration materials still remains a hot research topic due to the unmet clinical challenge of large bone defect healing. Bone grafting materials have gradually evolved from single component to multiple-component composite, but their functions during bone healing still only regulate one or two biological processes. Therefore, there is an urgent need to develop novel materials with more complex composition, which convey multiple biological functions during bone regeneration. Here, we report an naturally nanostructured ECM based composite scaffold derived from fish air bladder and combined with dicalcium phosphate (DCP) microparticles to form a new type of bone grafting material. The DCP/acellular tissue matrix (DCP/ATM) scaffold demonstrated porous structure with porosity over 65% and great capability of absorbing water and other biologics. In vitro cell culture study showed that DCP/ATM scaffold could better support osteoblast proliferation and differentiation in comparison with DCP/ADC made from acid extracted fish collagen. Moreover, DCP/ATM also demonstrated more potent bone regenerative properties in a rat calvarial defect model, indicating incorporation of ECM based matrix in the scaffolds could better support bone formation. Taken together, this study demonstrates a new avenue toward the development of new type of bone regeneration biomaterial utilizing ECM as its key components.

Physical and Chemical Factors Influencing the Printability of Hydrogel-based Extrusion Bioinks

Bioprinting researchers agree that "printability" is a key characteristic for bioink development, but neither the meaning of the term nor the best way to experimentally measure it has been established. Furthermore, little is known with respect to the underlying mechanisms which determine a bioink's printability. A thorough understanding of these mechanisms is key to the intentional design of new bioinks. For the purposes of this review, the domain of printability is defined as the bioink requirements which are unique to bioprinting and occur during the printing process. Within this domain, the different aspects of printability and the factors which influence them are reviewed. The extrudability, filament classification, shape fidelity, and printing accuracy of bioinks are examined in detail with respect to their rheological properties, chemical structure, and printing parameters. These relationships are discussed and areas where further research is needed, are identified. This review serves to aid the bioink development process, which will continue to play a major role in the successes and failures of bioprinting, tissue engineering, and regenerative medicine going forward.

Regenerative hepatology: In the quest for a modern prometheus?

As liver-related morbidity and mortality is rising worldwide and orthotopic liver transplantation (OLT) remains the only standard-of-care for end-stage liver disease or acute liver failure, shortage of donor organs is becoming more prominent. Importantly, advances in regenerative Hepatology and liver bioengineering are bringing new hope to the possibility of restoring impaired hepatic functionality in the presence of acute or chronic liver failure. Hepatocyte transplantation and artificial liver-support systems were the first strategies used in regenerative hepatology but have presented various types of efficiency limitations restricting their widespread use. In parallel, liver bioengineering has been a rapidly developing field bringing continuously novel advancements in biomaterials, three dimensional (3D) scaffolds, cell sources and relative methodologies for creating bioengineered liver tissue. The current major task in liver bioengineering is to build small implantable liver mass for treating inherited metabolic disorders, bioengineered bile ducts for congenital biliary defects and large bioengineered liver organs for transplantation, as substitutes to donor-organs, in cases of acute or acute-on-chronic liver failure. This review aims to summarize the state-of-the-art and upcoming technologies of regenerative Hepatology that are emerging as promising alternatives to the current standard-of care in liver disease.

Evaluation of Supercritical CO2-Assisted Protocols in a Model of Ovine Aortic Root Decellularization

One of the leading trends in the modern tissue engineering is the development of new effective methods of decellularization aimed at the removal of cellular components from a donor tissue, reducing its immunogenicity and the risk of rejection. Supercritical CO₂ (scCO₂)-assisted processing has been proposed to improve the outcome of decellularization, reduce contamination and time costs. The resulting products can serve as personalized tools for tissue-engineering therapy of various somatic pathologies. However, the decellularization of heterogeneous 3D structures, such as the aortic root, requires optimization of the parameters, including preconditioning medium composition, the type of co-solvent, values of pressure and temperature inside the scCO₂ reactor, etc. In our work, using an ovine aortic root model, we performed a comparative analysis of the effectiveness of decellularization approaches based on various combinations of these parameters. The protocols were based on the combinations of treatments in alkaline, ethanol or detergent solutions with scCO₂-assisted processing at different modes. Histological analysis demonstrated favorable effects of the preconditioning in a detergent solution. Following processing in scCO₂ medium provided a high decellularization degree, reduced cytotoxicity, and increased ultimate tensile strength and Young’s modulus of the aortic valve leaflets, while the integrity of the extracellular matrix was preserved.

Decellularised whole ovine testis as a potential bio-scaffold for tissue engineering

The aim of this study was to determine an efficient whole-organ decellularisation protocol of a human-sized testis by perfusion through the testicular arteries. In the first step of this study, we determined the most efficient detergent agent, whereas the second phase delineated the optimal time required for the decellularisation process. Initially sheep testes were decellularised by one of three different detergent agents: sodium dodecyl sulphate (SDS), Triton X-100 and trypsin-ethylenediamine tetraacetic acid (EDTA) solutions, each perfused for 6h. In the second phase, the selected detergent agent was applied for different time periods. A total number of 20 organs were processed during this investigation. The efficacy of the decellularisation process and the preservation of the extracellular matrix components and structure were evaluated by histopathological examinations, 4',6'-diamidino-2-phenylindole (DAPI) staining, DNA quantification, hydroxyproline measurement, magnetic resonance imaging and scanning electron microscopy. Organ perfusion with 1% SDS solution for 6 to 8h demonstrated the most desirable outcomes regarding decellularisation and extracellular matrix preservation. The 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay was used to determine the toxicity of the scaffold and its potential for further application in tissue-engineering investigations. This investigation introduces an efficient method to produce a three-dimensional testicular bio-scaffold resembling the properties of the native organ that could be employed in tissue-engineering studies.

In vivo application of decellularized rat colon and evaluation of the engineered scaffolds following 9 months of follow-up

The aim of this study was to investigate the rat small intestine mesentery and colon as natural bio-reactors for rat colon-derived scaffolds. We decellularized eight whole rat colons by a perfusion-based protocol using 0.1% sodium dodecyl sulfate for 24 hr. The provided bio-scaffolds were examined by histological staining, scanning electron microscopy, and collagen and sulfated glycosaminoglycan quantification. Subsequently, we implanted 4 cm segments of the provided bio-scaffolds into two groups of animal models comprising tissue grafting into the mesenteric tissue (n: 10) and end-to-end anastomosis (n: 10) to the colon of host rats. Following 9 months of follow-up, we harvested the grafts and performed histological and immunohistochemical studies as well as real-time PCR evaluation for telomerase activity of the samples. Histological staining, scanning electron microscopy and protein content evaluation of the acellular tissues confirmed the complete removal of the cellular components and preservation of the extracellular matrix. Histopathological assessment of the implanted scaffolds was suggestive of a regenerative process in both groups. Moreover, immunohistochemical analysis of the samples confirmed the presence of smooth muscle cells, endothelial progenitor cells, and neural elements in both groups of grafted scaffolds. Our data confirmed the recellularization of the acellular colon grafts in both groups after 9 months of follow up. Also, the implanted tissues demonstrated different characteristics based on their implantation location. The outcomes of this investigation illustrate the capability of acellular tissues for in vivo application and regeneration.

Applied Bioengineering in Tissue Reconstruction, Replacement, and Regeneration

IMPACT STATEMENT

The use of autologous tissue in the reconstruction of tissue defects has been the gold standard. However, current standards still face many limitations and complications. Improving patient outcomes and quality of life by addressing these barriers remain imperative. This article provides historical perspective, covers the major limitations of current standards of care, and reviews recent advances and future prospects in applied bioengineering in the context of tissue reconstruction, replacement, and regeneration.

A Novel Composite Hydrogel Composed of Formic Acid-Decellularized Pepsin-Soluble Extracellular Matrix Hydrogel and Sacchachitin Hydrogel as Wound Dressing to Synergistically Accelerate Diabetic Wound Healing

Extracellular matrix (ECM) hydrogel can create a favorable regenerative microenvironment and act as a promising dressing for accelerating the healing of diabetic wound. In this study, a simple and effective decellularization technique was developed and optimized to obtain acellular extracellular matrix (aECM) from porcine skin. It was found that decellularization at 30% formic acid for 72 h effectively decellularized porcine skin while retaining >75% collagen and ~37% GAG in the aECM with no presence of nuclei of cellular remnants. aECM hydrogel was fabricated by digesting aECM with pepsin in various acidic solutions (0.1 N HCl, glycolic acid (GA) and 2-pyrrolidone-5-carboxylic acid (PCA)) and then treated with a pH-controlled neutralization and temperature-controlled gelation procedure. Based on physical characterizations, including SDS-PAGE, rheological analysis and SEM analysis, aECM_HCl hydrogels fabricated at 25 mg/mL in 0.1 N HCl were selected. Four polymeric ECM-mimic hydrogels, including sacchachitin (SC), hyaluronic acid (HA) and chitosan (CS) and three composite hydrogels of combining SC either with aECM_HCl,25 (aECM_HCl/SC), HA (HA/SC) or CS (SC/CS) were prepared and evaluated for WS-1 cell viability and wound-healing effectiveness. Cell viability study confirmed that no hydrogel dressings possessed any toxicity at all concentrations examined and ECM_HCl, HA and ECM_HCl/SC at higher concentrations (>0.05%) induced statistically significant proliferation. Diabetic wound healing study and histological examinations revealed that ECM_HCl/SC hydrogel was observed to synergistically accelerate wound healing and ultimately stimulated the growth of hair follicles and sweat glands in the healing wound indicating the wound had healed as functional tissues. The results support the great potential of this newly produced ECM_HCl/SC composite hydrogel for healing and regeneration of diabetic wounds.

Extracellular matrix-based biomaterials for cardiac regeneration and repair

The spectrum of ischemic heart diseases, encompassing acute myocardial infarction to heart failure, represents the leading cause of death worldwide. Although extensive progress in cardiovascular diagnoses and therapy has been made, the prevalence of the disease continues to increase. Cardiac regeneration has a promising perspective for the therapy of heart failure. Recently, extracellular matrix (ECM) has been shown to play an important role in cardiac regeneration and repair after cardiac injury. There is also evidence that the ECM could be directly used as a drug to promote cardiomyocyte proliferation and cardiac regeneration. Increasing evidence supports that applying ECM biomaterials to maintain heart function recovery is an important approach to apply the concept of cardiac regenerative medicine to clinical practice in the future. Here, we will introduce the essential role of cardiac ECM in cardiac regeneration and summarize the approaches of delivering ECM biomaterials to promote cardiac repair in this review.

Comprehensive proteomic atlas of skin biomatrix scaffolds reveals a supportive microenvironment for epidermal development

Biomaterial scaffolds are increasingly being used to drive tissue regeneration. The limited success so far in human tissues rebuilding and therapy application may be due to inadequacy of the functionality biomaterial scaffold. We developed a new decellularized method to obtain complete anatomical skin biomatrix scaffold in situ with extracellular matrix (ECM) architecture preserved, in this study. We described a skin scaffold map by integrated proteomics and systematically analyzed the interaction between ECM proteins and epidermal cells in skin microenvironment on this basis. They were used to quantify structure and function of the skin's Matrisome, comprised of core ECM components and ECM-associated soluble signals that are key regulators of epidermal development. We especially revealed that ECM played a role in determining the fate of epidermal stem cells through hemidesmosome components. These concepts not only bring us a new understanding of the role of the skin ECM niche, they also provide an attractive combinational strategy based on tissue engineering principles with skin biomatrix scaffold materials for the acceleration and enhancement of tissue regeneration.

Tissue-engineered human embryonic stem cell-containing cardiac patches: evaluating recellularization of decellularized matrix

Decellularized cardiac extracellular matrix scaffolds with preserved composition and architecture can be used in tissue engineering to reproduce the complex cardiac extracellular matrix. However, evaluating the extent of cardiomyocyte repopulation of decellularized cardiac extracellular matrix scaffolds after recellularization attempts is challenging. Here, we describe a unique combination of biochemical, biomechanical, histological, and physiological parameters for quantifying recellularization efficiency of tissue-engineered cardiac patches compared with native cardiac tissue. Human embryonic stem cell-derived cardiomyocytes were seeded into rat heart atrial and ventricular decellularized cardiac extracellular matrix patches. Confocal and atomic force microscopy showed cell integration within the extracellular matrix basement membrane that was accompanied by restoration of native cardiac tissue passive mechanical properties. Multi-electrode array and immunostaining (connexin 43) were used to determine synchronous field potentials with electrical coupling. Myoglobin content (~60%) and sarcomere length measurement (>45% vs 2D culture) were used to evaluate cardiomyocyte maturation of integrated cells. The combination of these techniques allowed us to demonstrate that as cellularization efficiency improves, cardiomyocytes mature and synchronize electrical activity, and tissue mechanical/biochemical properties improve toward those of native tissue.

A Hepatic Scaffold from Decellularized Liver Tissue: Food for Thought

Allogeneic liver transplantation is still deemed the gold standard solution for end-stage organ failure; however, donor organ shortages have led to extended waiting lists for organ transplants. In order to overcome the lack of donors, the development of new therapeutic options is mandatory. In the last several years, organ bioengineering has been extensively explored to provide transplantable tissues or whole organs with the final goal of creating a three-dimensional growth microenvironment mimicking the native structure. It has been frequently reported that an extracellular matrix-based scaffold offers a structural support and important biological molecules that could help cellular proliferation during the recellularization process. The aim of the present review is to underline the recent developments in cell-on-scaffold technology for liver bioengineering, taking into account: (1) biological and synthetic scaffolds; (2) animal and human tissue decellularization; (3) scaffold recellularization; (4) 3D bioprinting; and (5) organoid technology. Future possible clinical applications in regenerative medicine for liver tissue engineering and for drug testing were underlined and dissected.

Methods to generate tissue-derived constructs for regenerative medicine applications

The shortage of donor organs for transplantation remains a continued problem for patients with irreversible end-stage organ failure. Tissue engineering and regenerative medicine aims to develop therapies to provide viable solutions for these patients. Use of decellularized tissue scaffolds has emerged as an attractive approach to generate tissue constructs that mimic native tissue architecture and vascular networks. The process of decellularization which involves the removal of resident cellular components from donor tissues has been successfully translated to the clinic for applications in patients. However, transplantation of bioengineered solid organs using this approach remains a challenge as the process requires repopulating target cells to achieve functioning organs. This article presents a comprehensive overview of the methods used to achieve decellularization, the types of decellularizing agents, and the potential cell sources that could be used to achieve tissue function. Understanding the mechanism of action of the decellularizing agent and the processing methods will provide the optimal results for applications.

Recent Trends in Decellularized Extracellular Matrix Bioinks for 3D Printing: An Updated Review

The promise of regenerative medicine and tissue engineering is founded on the ability to regenerate diseased or damaged tissues and organs into functional tissues and organs or the creation of new tissues and organs altogether. In theory, damaged and diseased tissues and organs can be regenerated or created using different configurations and combinations of extracellular matrix (ECM), cells, and inductive biomolecules. Regenerative medicine and tissue engineering can allow the improvement of patients' quality of life through availing novel treatment options. The coupling of regenerative medicine and tissue engineering with 3D printing, big data, and computational algorithms is revolutionizing the treatment of patients in a huge way. 3D bioprinting allows the proper placement of cells and ECMs, allowing the recapitulation of native microenvironments of tissues and organs. 3D bioprinting utilizes different bioinks made up of different formulations of ECM/biomaterials, biomolecules, and even cells. The choice of the bioink used during 3D bioprinting is very important as properties such as printability, compatibility, and physical strength influence the final construct printed. The extracellular matrix (ECM) provides both physical and mechanical microenvironment needed by cells to survive and proliferate. Decellularized ECM bioink contains biochemical cues from the original native ECM and also the right proportions of ECM proteins. Different techniques and characterization methods are used to derive bioinks from several tissues and organs and to evaluate their quality. This review discusses the uses of decellularized ECM bioinks and argues that they represent the most biomimetic bioinks available. In addition, we briefly discuss some polymer-based bioinks utilized in 3D bioprinting.

Naturally-Derived Biomaterials for Tissue Engineering Applications

Naturally-derived biomaterials have been used for decades in multiple regenerative medicine applications. From the simplest cell microcarriers made of collagen or alginate, to highly complex decellularized whole-organ scaffolds, these biomaterials represent a class of substances that is usually first in choice at the time of electing a functional and useful biomaterial. Hence, in this chapter we describe the several naturally-derived biomaterials used in tissue engineering applications and their classification, based on composition. We will also describe some of the present uses of the generated tissues like drug discovery, developmental biology, bioprinting and transplantation.

State-of-the-Art Strategies for the Vascularization of Three-Dimensional Engineered Organs

Engineering three-dimensional (3D) implantable tissue constructs is a promising strategy for replacing damaged or diseased tissues and organs with functional replacements. However, the efficient vascularization of new 3D organs is a major scientific and technical challenge since large tissue constructs or organs require a constant blood supply to survive in vivo. Current approaches to solving this problem generally fall into the following three major categories: (a) cell-based, (b) angiogenic factor-based, and (c) scaffold-based. In this review, we summarize state-of-the-art technologies that are used to develop complex, stable, and functional vasculature for engineered 3D tissue constructs and organs; additionally, we have suggested directions for future research.

Development of an efficient perfusion-based protocol for whole-organ decellularization of the ovine uterus as a human-sized model and in vivo application of the bioscaffolds

PURPOSE

The main purpose of this investigation was to determine an efficient whole-organ decellularization protocol of a human-sized uterus and evaluate the in vivo properties of the bioscaffold.

METHODS

Twenty-four ovine uteri were included in this investigation and were decellularized by three different protocols (n 6). We performed histopathological and immunohistochemical evaluations, 4,6-diamidino-2-phenylindole (DAPI) staining, DNA quantification, MTT assay, scanning electron microscopy, biomechanical studies, and CT angiography to characterize the scaffolds. The optimized protocol was determined, and patches were grafted into the uterine horns of eight female Wistar rats. The grafts were extracted after 10 days; the opposite horns were harvested to be evaluated as controls.

RESULTS

Protocol III (perfusion with 0.25% and 0.5% SDS solution and preservation in 10% formalin) was determined as the optimized method with efficient removal of the cellular components while preserving the extracellular matrix. Also, the bioscaffolds demonstrated native-like biomechanical, structural, and vascular properties. Histological and immunohistochemical evaluations of the harvested grafts confirmed the biocompatibility and recellularization potential of bioscaffolds. Also, the grafts demonstrated higher positive reaction for CD31 and Ki67 markers compared with the control samples which indicated eminent angiogenesis properties and proliferative capacity of the implanted tissues.

CONCLUSIONS

This investigation introduces an optimized protocol for whole-organ decellularization of the human-sized uterus with native-like characteristics and a prominent potential for regeneration and angiogenesis which could be employed in in vitro and in vivo studies. To the best of our knowledge, this is the first study to report biomechanical properties and angiographic evaluations of a large animal uterine scaffold.

A Photo-Crosslinkable Kidney ECM-Derived Bioink Accelerates Renal Tissue Formation

3D bioprinting strategies in tissue engineering aim to fabricate clinically applicable tissue constructs that can replace the damaged or diseased tissues and organs. One of the main prerequisites in 3D bioprinting is finding an appropriate bioink that provides a tissue-specific microenvironment supporting the cellular growth and maturation. In this respect, decellularized extracellular matrix (dECM)-derived hydrogels have been considered as bioinks for the cell-based bioprinting due to their capability to inherit the intrinsic cues from native ECM. Herein, a photo-crosslinkable kidney ECM-derived bioink (KdECMMA) is developed that could provide a kidney-specific microenvironment for renal tissue bioprinting. Porcine whole kidneys are decellularized through a perfusion method, dissolved in an acid solution, and chemically modified by methacrylation. A KdECMMA-based bioink is formulated and evaluated for rheological properties and printability for the printing process. The results show that the bioprinted human kidney cells in the KdECMMA bioink are highly viable and mature with time. Moreover, the bioprinted renal constructs exhibit the structural and functional characteristics of the native renal tissue. The potential of the tissue-specific ECM-derived bioink is demonstrated for cell-based bioprinting that could enhance the cellular maturation and eventually tissue formation.

Processing of collagen based biomaterials and the resulting materials properties

Collagen, the most abundant extracellular matrix protein in animal kingdom belongs to a family of fibrous proteins, which transfer load in tissues and which provide a highly biocompatible environment for cells. This high biocompatibility makes collagen a perfect biomaterial for implantable medical products and scaffolds for in vitro testing systems. To manufacture collagen based solutions, porous sponges, membranes and threads for surgical and dental purposes or cell culture matrices, collagen rich tissues as skin and tendon of mammals are intensively processed by physical and chemical means. Other tissues such as pericardium and intestine are more gently decellularized while maintaining their complex collagenous architectures. Tissue processing technologies are organized as a series of steps, which are combined in different ways to manufacture structurally versatile materials with varying properties in strength, stability against temperature and enzymatic degradation and cellular response. Complex structures are achieved by combined technologies. Different drying techniques are performed with sterilisation steps and the preparation of porous structures simultaneously. Chemical crosslinking is combined with casting steps as spinning, moulding or additive manufacturing techniques. Important progress is expected by using collagen based bio-inks, which can be formed into 3D structures and combined with live cells. This review will give an overview of the technological principles of processing collagen rich tissues down to collagen hydrolysates and the methods to rebuild differently shaped products. The effects of the processing steps on the final materials properties are discussed especially with regard to the thermal and the physical properties and the susceptibility to enzymatic degradation. These properties are key features for biological and clinical application, handling and metabolization.

The analysis of the proliferative activity of cells on microparticles obtained from decellularized liver and kidney tissue

Aim.To develop the protocols for liver and kidney tissue decellularization, and to develop an analysis of the proliferative activity of human Hep-G2hepatocarcinoma cells on various carriers.

Materials and methods.Decellularization of the liver and kidneys was performed by perfusion of detergent solutions with gradually increasing concentrations of Triton X-100 (1, 2 and 3%). A histological analysis of the obtained samples was performed, and the method of optical and scanning electron microscopy was used to study the obtained samples. The proliferative activity of human Hep-G2hepatocarcinoma cells was studied on the obtained samples of decellularized liver and kidney tissue.

Results.Decellularization of the organ does not lead to changes in the specific structure of the tissue matrix. Microparticles with an average size of 200 μm were made from their decellularized matrix of liver and kidney tissues. The level of proliferative activity of human Hep-G2hepatocarcinoma cells cultured on microparticles from a decellularized liver was significantly higher than on microparticles from a decellularized kidney.

Conclusion.The decellularized matrix retains the native three-dimensional structure of the tissue. The level of cell proliferative activity is significantly higher on microparticles from the decellularized liver, which confirms the preservation of the specificity of the extracellular matrix of the tissue after the process of decellularization.